[jira] [Created] (KAFKA-8846) Unexpected results joining a KStream to a KTable after repartitioning

["Thomas Crowley (Jira)" <ji...@apache.org>]

Thomas Crowley created KAFKA-8846:
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             Summary: Unexpected results joining a KStream to a KTable after repartitioning 
                 Key: KAFKA-8846
                 URL: https://issues.apache.org/jira/browse/KAFKA-8846
             Project: Kafka
          Issue Type: Bug
          Components: streams
    Affects Versions: 2.3.0
            Reporter: Thomas Crowley


We seem to have come across a bug with Kafka Streams (or at least unexpected behavior) when joining a KStream to a KTable after re-partitioning our data (via `selectKey`)

Our use case is as follows: we want to aggregate some values and join them back onto the original message, so that we emit the original message, joined with the current value of the aggregation at the current point in time.

Currently, without re-partitioning, we get the correct behavior as expected, but rekeying the input of the stream gives us incorrect results.

What's stranger, is that the `TestTopologyDriver` gives us the correct/expected results in our re-partitioned topology.


Apologies if Clojure is foreign to anyone, but I have an example of the problematic topology here:
https://github.com/VerrencyOpenSource/repartition-bug/blob/master/src/repartition_bug/with_repartition.clj#L27

If you have `lein` installed on your machine, I have instructions on how you can run the above topology against both the test topology driver and a Kafka cluster: 
https://github.com/VerrencyOpenSource/repartition-bug 





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